Istanbul fireworks blast kills 20 (Video)

Two explosions at an unlicensed fireworks factory in Istanbul have killed at least 20 people and injured dozens, Turkish officials say.

The blasts, at just after 0930 (0730 GMT), caused part of the five-storey building in the western Davutpasha district to collapse.

Rescuers working at the scene said there were no further signs of life from beneath the rubble.

The authorities have ruled out terrorism as the cause of the blast.

City officials said a fireworks factory had been operating in the building for more than two years without a licence.

Mayor Kadir Topbas said the first blast sparked a fire that drew onlookers, and minutes later there was a second explosion, which is when most of the victims are thought to have been injured of killed.

"White smoke was rising into the sky from the factory as we came to the front of the building. People were running around," a witness, who identified himself as Ali, told CNN Turk television.

Witness Ahmet Unal told Anatolia news agency that the walls of the building "began to swell from the pressure".

"There was a big bang and the building collapsed," he said.

The surrounding streets were covered with shattered glass, metal and chunks of concrete.

Television pictures broadcast immediately after the blast showed survivors carrying the injured out of the building.

A number of people were taken to hospital.

A similar explosion at a fireworks factory in 2006 killed six people but the BBC's Sarah Rainsford in Istanbul says this is by far the most serious accident of its kind for some time.